The Major Field Test in Business (MFT-B), a standardized assessment test of business knowledge among undergraduate business seniors, is widely used to measure student achievement. Many previous studies analyzing scores on the MFT-B report gender differences on the exam even after controlling for student's aptitude, general intellectual ability, and motivation. The authors' results point to two reasons behind this phenomenon. First, it is important to control for critical thinking abilities while explaining variation in MFT-B scores. Second, motivation to perform well on the test varies between genders and high- and low-performing students. (Contains 5 tables.)